<?php
/**
 * TMDO_Term_Comment_Shadow_Verifier — Sample-and-compare flat vs wp_*meta
 * for term + comment entities (v2.12.5 Phase 5).
 *
 * Mirror of TMDO_Post_Shadow_Verifier (v2.10.3). Used during shadow_read mode
 * to verify the flat tables stay in sync with wp_termmeta / wp_commentmeta.
 * Each sample picks a random entity + key, fetches both values, counts
 * matches / diffs / missing rows. Divergent values are written to
 * `wpdo_shadow_diffs` via TMDO_Shadow_Diff_Logger (entity_type-aware).
 *
 * Run pattern:
 *   - Manual: `wp wpdo term-comment-shadow-report`
 *   - Cron:   wpdo_term_comment_shadow_verify event registered when EITHER
 *             term or comment mode is shadow_read; auto-unregistered when
 *             both modes are not shadow_read
 *
 * 🔒 Frozen contract: read-only verifier. Never modifies wp_termmeta /
 * wp_commentmeta or flat tables.
 *
 * @package WP_Data_Optimizer
 * @since   2.12.5
 */

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

// phpcs:disable WordPress.DB.DirectDatabaseQuery.DirectQuery,WordPress.DB.DirectDatabaseQuery.NoCaching,WordPress.DB.PreparedSQL.InterpolatedNotPrepared,WordPress.DB.PreparedSQL.NotPrepared -- Internal verifier: $flat_table comes from registry, columns sanitized via Schema_Manager, user values use prepare(). Read-only.

/**
 * Sample-and-compare verifier for term + comment entity flat tables.
 */
final class TMDO_Term_Comment_Shadow_Verifier {

	/** Cron event hook fired hourly when at least one of term/comment modes is shadow_read. */
	public const CRON_HOOK = 'wpdo_term_comment_shadow_verify';

	/** Default sample size per entity per cron tick. */
	public const DEFAULT_SAMPLE_SIZE = 100;

	/**
	 * Group → flat table suffix mapping. Keep in sync with
	 * TMDO_Hivepress_Term_Comment_Fields registrations and the misc bucket.
	 *
	 * @var array<string, array{entity_type:string, table_suffix:string, has_misc:bool}>
	 */
	private const GROUP_MAP = array(
		'hp_taxonomy' => array(
			'entity_type'  => 'term',
			'table_suffix' => 'wpdo_term_hp_taxonomy',
		),
		'hp_review'   => array(
			'entity_type'  => 'comment',
			'table_suffix' => 'wpdo_comment_hp_review',
		),
	);

	/**
	 * Run a sample-compare pass for a single entity group.
	 *
	 * @param string   $entity_type 'term' or 'comment'.
	 * @param string   $group_name  Entity group name.
	 * @param string   $flat_table  Fully-qualified flat table name.
	 * @param string[] $keys        Meta keys to compare.
	 * @param int      $sample_size Number of entities to sample.
	 * @return array{
	 *   sampled:int,
	 *   matched:int,
	 *   diffs:int,
	 *   missing_flat:int,
	 *   missing_meta:int,
	 *   group:string,
	 *   entity_type:string,
	 * }
	 * @throws InvalidArgumentException When inputs invalid.
	 */
	public static function sample_compare(
		string $entity_type,
		string $group_name,
		string $flat_table,
		array $keys,
		int $sample_size = self::DEFAULT_SAMPLE_SIZE
	): array {
		if ( ! in_array( $entity_type, array( 'term', 'comment' ), true ) ) {
			$msg = 'entity_type must be term or comment';
			throw new InvalidArgumentException( $msg ); // phpcs:ignore WordPress.Security.EscapeOutput.ExceptionNotEscaped
		}
		if ( $sample_size <= 0 ) {
			$msg = 'Sample size must be > 0';
			throw new InvalidArgumentException( $msg ); // phpcs:ignore WordPress.Security.EscapeOutput.ExceptionNotEscaped
		}
		if ( empty( $keys ) ) {
			$msg = 'Keys array cannot be empty';
			throw new InvalidArgumentException( $msg ); // phpcs:ignore WordPress.Security.EscapeOutput.ExceptionNotEscaped
		}

		global $wpdb;

		// Source table + id column + meta table differ per entity type.
		if ( 'term' === $entity_type ) {
			$source_table  = $wpdb->terms;
			$source_id_col = 'term_id';
			$meta_table    = $wpdb->termmeta;
			$meta_id_col   = 'term_id';
			$flat_id_col   = 'term_id';
		} else {
			$source_table  = $wpdb->comments;
			$source_id_col = 'comment_ID';
			$meta_table    = $wpdb->commentmeta;
			$meta_id_col   = 'comment_id';
			$flat_id_col   = 'comment_id';
		}

		$ids = $wpdb->get_col(
			$wpdb->prepare(
				"SELECT `{$source_id_col}` FROM `{$source_table}` ORDER BY RAND() LIMIT %d",
				$sample_size
			)
		);

		$sampled      = count( $ids );
		$matched      = 0;
		$diffs        = 0;
		$missing_flat = 0;
		$missing_meta = 0;

		if ( 0 === $sampled ) {
			return array(
				'sampled'      => 0,
				'matched'      => 0,
				'diffs'        => 0,
				'missing_flat' => 0,
				'missing_meta' => 0,
				'group'        => $group_name,
				'entity_type'  => $entity_type,
			);
		}

		foreach ( $ids as $object_id ) {
			$object_id = (int) $object_id;
			foreach ( $keys as $key ) {
				$col      = self::sanitize_column( $key );
				$flat_val = $wpdb->get_var(
					$wpdb->prepare(
						"SELECT `{$col}` FROM `{$flat_table}` WHERE `{$flat_id_col}` = %d LIMIT 1",
						$object_id
					)
				);
				$meta_val = $wpdb->get_var(
					$wpdb->prepare(
						"SELECT meta_value FROM `{$meta_table}` WHERE `{$meta_id_col}` = %d AND meta_key = %s LIMIT 1",
						$object_id,
						$key
					)
				);

				$flat_present = null !== $flat_val && '' !== $flat_val;
				$meta_present = null !== $meta_val && '' !== $meta_val;

				// In-memory counters only. Hook Bus auto-logs diffs to
				// wpdo_shadow_diffs on every read in shadow_read mode (via
				// TMDO_Shadow_Diff_Logger::compare_and_log) — this verifier
				// is a sample-based snapshot, not the persistent log.
				if ( ! $flat_present && ! $meta_present ) {
					++$matched;
					continue;
				}
				if ( ! $flat_present && $meta_present ) {
					++$missing_flat;
					continue;
				}
				if ( $flat_present && ! $meta_present ) {
					++$missing_meta;
					continue;
				}

				if ( self::values_loose_equal( $meta_val, $flat_val ) ) {
					++$matched;
				} else {
					++$diffs;
				}
			}
		}

		return array(
			'sampled'      => $sampled,
			'matched'      => $matched,
			'diffs'        => $diffs,
			'missing_flat' => $missing_flat,
			'missing_meta' => $missing_meta,
			'group'        => $group_name,
			'entity_type'  => $entity_type,
		);
	}

	/**
	 * Cron handler: runs sample_compare for every group whose entity is in
	 * shadow_read. No-op when neither term nor comment is shadow_read.
	 *
	 * @return void
	 */
	public static function cron_tick(): void {
		if ( ! class_exists( 'TMDO_Mode_Manager' ) ) {
			return;
		}
		$term_shadow    = 'shadow_read' === TMDO_Mode_Manager::get( 'term' );
		$comment_shadow = 'shadow_read' === TMDO_Mode_Manager::get( 'comment' );
		if ( ! $term_shadow && ! $comment_shadow ) {
			return;
		}
		if ( ! class_exists( 'TMDO_Entity_Registry' ) ) {
			return;
		}

		global $wpdb;

		foreach ( self::GROUP_MAP as $group => $cfg ) {
			$entity_type = $cfg['entity_type'];

			// Only run when the entity is in shadow_read mode.
			if ( 'term' === $entity_type && ! $term_shadow ) {
				continue;
			}
			if ( 'comment' === $entity_type && ! $comment_shadow ) {
				continue;
			}

			$keys = TMDO_Entity_Registry::get_group_keys( $entity_type, $group );
			if ( empty( $keys ) ) {
				continue;
			}
			$flat_table = $wpdb->prefix . $cfg['table_suffix'];

			try {
				self::sample_compare( $entity_type, $group, $flat_table, $keys, self::DEFAULT_SAMPLE_SIZE );
			} catch ( \Throwable $e ) {
				if ( class_exists( 'TMDO_Logger' ) ) {
					TMDO_Logger::error(
						'term_comment_shadow_verifier',
						'cron_tick',
						$e->getMessage()
					);
				}
			}
		}
	}

	/**
	 * Recent diff records for term + comment entity types.
	 *
	 * @param int $limit Max rows.
	 * @return array
	 */
	public static function recent_diffs( int $limit = 100 ): array {
		if ( ! class_exists( 'TMDO_Shadow_Diff_Logger' ) ) {
			return array();
		}

		// Logger is entity-type-aware; gather both sides.
		$term_diffs    = TMDO_Shadow_Diff_Logger::recent( (int) ceil( $limit / 2 ), 'term' );
		$comment_diffs = TMDO_Shadow_Diff_Logger::recent( (int) ceil( $limit / 2 ), 'comment' );

		return array_merge( (array) $term_diffs, (array) $comment_diffs );
	}

	/**
	 * Aggregate diff stats for term+comment over recent N hours.
	 *
	 * @param int $hours Window (default 24).
	 * @return array{total:int,term:int,comment:int,by_key:array<string,int>}
	 */
	public static function diff_stats( int $hours = 24 ): array {
		global $wpdb;
		$table = $wpdb->prefix . 'wpdo_shadow_diffs';

		$exists = (bool) $wpdb->get_var(
			$wpdb->prepare( 'SHOW TABLES LIKE %s', $table )
		);
		if ( ! $exists ) {
			return array(
				'total'   => 0,
				'term'    => 0,
				'comment' => 0,
				'by_key'  => array(),
			);
		}

		$since = gmdate( 'Y-m-d H:i:s', time() - ( $hours * HOUR_IN_SECONDS ) );

		$term_total    = (int) $wpdb->get_var(
			$wpdb->prepare(
				"SELECT COUNT(*) FROM `{$table}` WHERE entity_type = 'term' AND ts >= %s",
				$since
			)
		);
		$comment_total = (int) $wpdb->get_var(
			$wpdb->prepare(
				"SELECT COUNT(*) FROM `{$table}` WHERE entity_type = 'comment' AND ts >= %s",
				$since
			)
		);

		$rows = $wpdb->get_results(
			$wpdb->prepare(
				"SELECT meta_key, COUNT(*) AS n FROM `{$table}` WHERE entity_type IN ('term','comment') AND ts >= %s GROUP BY meta_key ORDER BY n DESC",
				$since
			),
			ARRAY_A
		);

		$by_key = array();
		foreach ( (array) $rows as $row ) {
			$by_key[ (string) $row['meta_key'] ] = (int) $row['n'];
		}

		return array(
			'total'   => $term_total + $comment_total,
			'term'    => $term_total,
			'comment' => $comment_total,
			'by_key'  => $by_key,
		);
	}

	/**
	 * Run sample_compare for ALL groups (regardless of mode). Used by
	 * `wp wpdo term-comment-shadow-report` so users can see drift even
	 * before promoting to shadow_read.
	 *
	 * @param int $sample_size Per-group sample size.
	 * @return array<string,array> Map of `group_name` → sample_compare() result.
	 */
	public static function run_all( int $sample_size = self::DEFAULT_SAMPLE_SIZE ): array {
		if ( ! class_exists( 'TMDO_Entity_Registry' ) ) {
			return array();
		}

		global $wpdb;
		$out = array();

		foreach ( self::GROUP_MAP as $group => $cfg ) {
			$entity_type = $cfg['entity_type'];
			$keys        = TMDO_Entity_Registry::get_group_keys( $entity_type, $group );
			if ( empty( $keys ) ) {
				continue;
			}
			$flat_table = $wpdb->prefix . $cfg['table_suffix'];

			try {
				$out[ $group ] = self::sample_compare( $entity_type, $group, $flat_table, $keys, $sample_size );
			} catch ( \Throwable $e ) {
				$out[ $group ] = array(
					'error' => $e->getMessage(),
					'group' => $group,
				);
			}
		}

		return $out;
	}

	// ─────────────────────────────────────────────────────────────────────────
	// Helpers
	// ─────────────────────────────────────────────────────────────────────────

	/**
	 * Sanitize meta_key into a column name (mirrors Schema_Manager rules).
	 *
	 * @param string $key Meta key.
	 * @return string
	 */
	private static function sanitize_column( string $key ): string {
		if ( class_exists( 'TMDO_Schema_Manager' ) ) {
			return TMDO_Schema_Manager::sanitize_column_name( $key );
		}
		return preg_replace( '/[^a-zA-Z0-9_]/', '_', $key );
	}

	/**
	 * Loose equality for verifier — handles type widening and serialization
	 * format differences. Layers fail-fast: identical → numeric → decoded.
	 *
	 * @param mixed $a Side A value.
	 * @param mixed $b Side B value.
	 * @return bool
	 */
	private static function values_loose_equal( $a, $b ): bool {
		// 1. Identical strings.
		if ( (string) $a === (string) $b ) {
			return true;
		}
		// 2. Numeric loose match.
		if ( is_numeric( $a ) && is_numeric( $b ) && (float) $a === (float) $b ) {
			return true;
		}
		// 3. Decoded match (serialized vs JSON).
		$decoded_a = self::decode_value( (string) $a );
		$decoded_b = self::decode_value( (string) $b );
		return $decoded_a === $decoded_b;
	}

	/**
	 * Decode a stored value: try unserialize → JSON decode → as-is.
	 *
	 * @param string $value Raw stored value.
	 * @return mixed
	 */
	private static function decode_value( string $value ) {
		// Try unserialize for postmeta-style serialized payloads.
		if ( '' !== $value ) {
			$first_two = substr( $value, 0, 2 );
			if ( 'a:' === $first_two || 'O:' === $first_two || 's:' === $first_two || 'i:' === $first_two || 'b:' === $first_two || 'd:' === $first_two ) {
				$unserialized = @unserialize( $value, array( 'allowed_classes' => false ) ); // phpcs:ignore WordPress.PHP.DiscouragedPHPFunctions.serialize_unserialize,WordPress.PHP.NoSilencedErrors
				if ( false !== $unserialized || 'b:0;' === $value ) {
					return $unserialized;
				}
			}
		}
		// Try JSON for flat-table json-typed columns.
		if ( '' !== $value && ( '{' === $value[0] || '[' === $value[0] ) ) {
			$json = json_decode( $value, true );
			if ( null !== $json ) {
				return $json;
			}
		}
		return $value;
	}
}